In a statement to SBS News, the Department of Home Affairs said it had "engaged a new health services provider from 1 May 2018 (and) IHMS will work with the new health service provider during a transition period".

"Individuals will continue to have access to appropriate primary health services," it said.

A spokesperson from IHMS confirmed the April 30 end date but said "it will, however, maintain a core group of staff in Manus and Port Moresby to support the transition to a new health service provider".

But neither the Department of Home Affairs or IHMS would say who the new provider is, leaving open questions about the quality of the care.

Greens senator Nick McKim told SBS News Australians are once again "in the dark" about the treatment of refugees on Manus.

Mr McKim said getting information from the Department of Home Affairs was "like getting blood from a stone".